Wednesday, January 3, 2018

Test of Chameleon CHA MPAS Antenna

I recently picked up a Chameleon CHA MPAS antenna with the Mil Extension (CHA MIL EXT), and their ground spike for portable & SOTA
work. The primary reason is that
sometimes, the summit is going to be too busy with people to setup my dipole
rig. Cowles mtn is a good example. Another reason is that I may want the option
of setting up faster (5 minutes) rather than goofing around with the
dipole. Mountain tops here don’t have
trees so my dipole setup is a mast, guys, and an inverted V config.

I wanted to do a quick setup and function test
before my next hike to my main test area (Black Mtn.) or the next SOTA mountain
that I want to check off. My initial
testing was at a park on the top of a hill (Hilltop Park) in San Diego. I setup at two different areas and used a Rigexpert 600 antenna analyzer to gather the
data. I mainly focused on 20 & 40
meter bands and I wanted to know how tunable the antenna was and if I could get
out. The bands weren’t busy and I was
wondering if the antenna was going to work at all. My opinion changed when I had a quick QSO
with a guy in Puerto Rico, Vancouver, and another in Nevada. I guess it’s working.

Note: I’m a newbie at this (licensed
general about 3 months ago) so if you find any errors or have any suggestions,
comments, etc, I’d really appreciate you
commenting below.

One other note. The SWR readings are from the graph are
estimates based on the graph visual (supplied) and not exact readings except
for the median freq. I could have taken
a reading at each end but I really didn’t feel it was needed. Also, the analyzer is new but I’ve never had
it calibrated or bench tested. I could have the most exact data in the world
but the data variations produced by different soil, moving the counterpoise
just a little, and the way I had my tongue hanging all bump my test results one
way or another. As a ham, you know that
there are about a 1000+ other variables that come into play during actual
use. My sample data has three points and
it is directionally correct.
Reproducing the tests at three
sites were pretty much +- .2 SWR. The
analyzer pictures have additional data that I did not cover. Take a look and let me know your
thoughts.

I tested three different configurations in
three locations (2 at the park and one at my house) and one config at a single location. All configurations have a single counterpoise
because that is my intended SOTA setup.

●One test with no matching unit,
just the 14’ of stick mounted on the bracket and a counterpoise.

The 7 MHZ band SWR when mounted at 14 feet on
the tripod’ ranged from 1.8 at the
bottom of the band to 1.95 at the top and was at 1.9 SWR in the middle.
Testing in the other two locations was within +- .2 SWR with my house
being lower.

The 14 MHZ band SWR when mounted at 14 feet
was from about 1.28 at the bottom of the band to 1.21 at the top and was at 1.26
SWR in the middle. Testing in the other two locations was within +- .2 SWR
with my house being lower.

I’m not going to bother showing the difference
between 14 and 6 feet because the data is +- .2 SWR. I did find that my house is consistently
lower but noticed that just changing the position of the counterpoise bumped
the results a bit. It’s also possible
that the soil, which is dry compared to the park, may have had some influence.

Sticking
this thing in the ground also works well, which really
surprised me. I’m guessing actual
performance won’t be the best, but for gun and run it will get the job done.

I did do a test of the 6M band (50 MHZ), and 80m (3 MHZ) and both are definitely tunable,
as you can see below.

My final test was to see if it would be
tunable without the matching unit. As
you can see below, the 20m band was tunable (I used a MFJ-939Y tuner), but the tuner wouldn’t bring
in the 40m band. When the tuner gave me
the warning song when trying to tune 40m, I didn’t bother hitting the radio
SWR.

I’m happy with 20m and 40m. Those test results are not only tunable, they
show that I can get by without an antenna tuner for this config. I made a couple of QSOs without the auto-tuner
and made Puerto Rico just as the band was headed south.

I did a bunch of research when looking at
end-fed verticals. The biggest
influencer was Julian at Survivaltech Nord, OH8STN.org.
His YouTube videos covered the Chameleon and Alpha antennas in
depth. I’m happy with the CHA MPAS,
it lives up to his review as far as
portability, build quality, etc. Yes,
I’ve only put it through one test (3 setup / breakdowns) but I think this is going to work out
great. I considered the Alpha and
dropped that idea after I saw his review and some others. I also considered the superantenna that
Julian is currently reviewing (I think he has three videos of it) but I took it
off the list because it was heavy and I didn’t want to futz with the tuner on
the loading coil when on a mission. For
SOTA work, I mainly work 20 and need the 40 meter when conditions are bad. The
CHA MPAS seems to do both easily (I wish I had done a QSO on 40m but I ran out
of time). I’ll do that in the next week.

Summary of tests and what I
learned:

The
antenna tunes for 20 and 40 for SOTA without a tuner. I’ll keep a tuner with me incase my
config gets strange. It is
definitely tunable on 6m and other bands.

Performance
was great (3,252 miles), and it went a lot farther than I thought. I consider the Chameleon a suboptimal
solution as compared to my Packtenna inverted V config but I may change my
mind after a couple of missions.
The compromise here for me is setup time, weight, and goofing
around. High winds could be a
issue, especially if they are swirling.

I’m
still learning how to evaluate capability of different antennas since
there is more to it than SWR. The
mission here was to see how tunable the antenna was and I checked that off
the list. Obviously I wanted to do
a quick QSO to validate the darn thing will get me out of the state, and I
checked that off.

The
matching unit really rocks and makes this system a real performer. Without the matching unit... well, it’s
just a wire in the air like anything else.
I’m not really sure why they give you the bracket to mount just the
antenna without the matching unit.
I’m only guessing but if you tune and can punch directly to the
wire without the matching unit, it may product a tad better results.

I
wish I had tested without the MIL EXT on it but I’m a bit of a freak and
figured that I would probably not run without it.

I
have a lot more to learn, that I think will only come with time.

This is the first shot I’ve taken at doing any
kind of published testing that should be reproducible and pass a peer review
since I’m using an empirical approach. I
did this because I wanted to give something back. As a new Ham, one of the things that is
really difficult for me is evaluating the difference in performance (actual
use, not SWR) between different
antennas, dipole and the vertical setup in this case. I know that the dipole is the gold standard
(yes, yagi and other directional are top dog but not for SOTA work). I like to maximize my DX when on the mountain
and I’d love to know how much I’m compromising.
When I skip 3,200 miles on my first time out, I guess I really shouldn’t
bitch. I do SOTA mainly because living
in a neighborhood means that my home station is one giant compromise. I have a clear shot to the east off the top
of the hill from my house via a 45’ gap (between houses). If it weren’t so unsightly for my neighbors,
I’d get something above my roofline. If
I did, I could get a good 270 deg beam shot off my hill.

If you have any thoughts on my analysis,
performance of the this vertical vs. dipole, comment below. I’d love to hear from you.

Super big thanks to K7CAR for allowing me to butt in during his CQ time
and connect with WP4CTD in Puerto Rico.
Kent also came back to me two more times as I was testing different
locations. This was super helpful and
fun.

2 comments:

Nice write up. Found your blog doing a search for "CHA MPAS SWR Chart". My 30ft mast and EFHW Wire had to come down since guy wires took a beating from my Alaskan Shepherds' jaws of life. Looking at a vertical for low angle take off on the lower bands, need antenna for next 9 months until I start the tower project. Welcome to ham radio. I was recently licensed in March 2017. 73, W7DAZ. Derek

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Chris Claborne is incredibly curious about technology, people and the world and is always trying to understand how things work. He's a "Technology Geek". The internet is fascinating place to learn, interact and watch from a technology perspective. He has 23+ years in IT for Fortune 500 companies and a specific interests in Cloud Computing.
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